This invention pertains to slurry valves, and in particular to slide gate valves designed especially for handling of high-density slurries, and to a valve body assembly, and a solids-containing wall lining means, for use in such gate valves.
Valves used in slurry service are subject to problems with the buildup of the slurry in cavities of the valve body, and jamming of the valve closure member, preventing the valve from opening or closing. Knife gate valves, and slide gate valves are some of the valves which are least susceptible to this problem, and are many times used in slurry service. The type of valve which is used depends upon the solids concentration, flowability of the solids, and the tendency of the solids to settle and pack in cavities. Knife gate valves rely on the cutting edge of the blade to pass through the solid materials. Slide gate valves have a through-ported gate, a gate with a round portway through which the material flows when the gate is in an open position. As the valve is closed, the gate portway moves through the slurry and displaces the solids, and does not cut through the solids. The knife gate is used when the solids are in low concentrations and flowable. The slide gate valve is used when the slurry is of high density or tends to settle and pack, and a knife gate will not cut through the solids.
For applications where the slurry has an extreme tendency to pack and solidify, slide gate valves utilize portway sealing, when in an open or closed position, so that the slurry does not enter the valve body. The body is not a pressure-containing member, so any solids escaping past the primary portway seal, during cycling, are allowed to spill out of the body, and not collect in body crevasses. This eliminates the chance for solids buildup in areas that prevent the valve gate from operating, but has the shortcoming of allowing the slurry media to spill into the environment.
Other versions of the slide gate valve have slurry-containing, sealed bodies to prevent spillage, but have the shortcoming of leakage of the slurry into body cavities, during cycling, that causes jamming of the valve closure member. A solution, to prevent the solids buildup from jamming, is to use flushports located in the body walls to flush out the solids from critical body cavities. This approach has the shortcomings of requiring flushing lines to be piped to the valve, and a control system to control the flow of flushing media. Also, many processes can not allow for the dilution or contamination of the flushing media in the process media.
A preferred valve, for high-density slurry, will have a gate and seal design which will (a) contain the solids from leaking externally, and (b) also prevent the solids from building up in valve body cavities, this without a need for flushing.
To avoid the aforecited shortcomings and limitations of performance, it is an object of this invention to set forth a slide gate valve for high-density slurries, comprising a valve body having (a) a plurality of mutually confronting, parallel walls, and (b) a chamber, therewithin, formed by said walls; wherein a pair of said confronting walls have apertures formed therein; and a gate disposed in said chamber for reciprocation therein, between said pair of walls, for occluding and exposing said apertures; first means, coupled to said gate for effecting reciprocation of said gate; second means, arranged in said chamber, for (a) engaging opposite sides of said gate, and (b) prohibiting an entry of slurry solids into said chamber; and means engaging said pair of walls for urging said second means into fast, sealing engagement with said gate.
It is also an object of this invention to disclose a valve body assembly, for use in a gate valve for high-density slurries, comprising a valve body having (a) a plurality of mutually confronting, parallel walls, and (b) a chamber, therewithin, formed by said walls; wherein a pair of said walls have apertures formed therein; lining means, arranged in said chamber, in parallel with said pair of walls, for engaging opposite sides of a valving gate, and for prohibiting, in cooperation with such a valving gate, an entry of slurry solids into said chamber; and means engaging said pair of walls for urging said lining means into a fast, sealing engagement with such a valving gate.
Further, it is an object of this invention to set forth, for use in a gate valve having a body with a chamber formed therein by a plurality of walls, wall lining means for cooperation with a valving gate, for prohibiting an entry of solids into said chamber, comprising panels of plastic, flexible material for arrangement in said chamber, in parallel with a pair of said walls, and for engaging opposite sides of a valving gate; and wherein said panels each have a layer of elastomeric material integral therewith.